In the process of acquiring a signal with microphones, there is the general problem that disturbances are superimposed on the wanted signal. This is valid particularly if the wanted signal is a speech signal. Then, the disturbances may influence the communication over communication devices, e.g. telephones or hands-free communication devices. The capability of speech recognition software may be influenced to the negative by these disturbances.
In principle, prior art methods for reducing noise work in such a way that the disturbances in the input signal are estimated, and then, the estimated disturbances are removed from the input signal.
In particular, some multi-channel methods are described in the literature, using a beamformer in connection with an postfilter, wherein the postfilter is used to remove the disturbances which have been determined based on information from the multi-channel part.
A prior art system working differently is described by E. Habets, S. Gannot: Dual-Microphone Speech Dereverberation using a Reference Signal. In: Proc IEEE Int. Conf. Acoust., Speech, Signal Processing (ICASSP-07), Honolulu, Hawai, USA, 2007.
At the present, those methods which remove the estimated disturbances from the input signal have the disadvantage that playing back the output signal gives an unnatural sound impression, particularly if the wanted signal is a speech signal. Practical solutions which can be applied robustly are not yet in the state of the art.